With the increased use of linear motion bearings in machinery and other applications, it has become desirable to decrease both the cost of the bearings as well as the cost of installations. Examples of linear motion bearings in the prior art include: Magee, U.S. Pat. No. 2,628,135; Magee and Thomson, U.S. Pat. No. 3,545,826; and Thomson, U.S. Pat. No. 3,588,200. These linear motion bearings are of the recirculating ball type in which the ball bearings travel in a generally elliptical path. One straight run portion of the path functions as a load bearing portion and the other straight run path is a non-load carrying portion.
When linear motion bearings are used in applications requiring more than one bearing, it will be appreciated that time consuming accurate mounting of the bearings relative to the shaft on which the bearing will ride is of great importance. Lubrication of the bearings presents serious problems in long stroke applications since a certain amount of lubricant tends to be carried on the shaft past the seals. This loss of lubricant results in the necessity of replenishing the lubricant at periodic intervals.
While the lubrication problem is somewhat alleviated by the use of lubricant impregnated ball retainers, such as disclosed in Magee and Thomson U.S. Pat. No. 3,545,826, bearing contamination due to material carried on the shaft has required the use of wiping seals at each end of the bearing. In applications where a plurality of linear bearings are required, the use of these wiping seals produces undesirable drag in many applications where minimal friction is essential.